In distillation processes, it is common practice to compress the gas mixture and then purify it in a purification system (for example an adsorption system) which needs to be regenerated after it has operated for some time, by passing through it a gas which is heated to the regeneration temperature. In the case of air, the adsorbent bottles which constitute the adsorption system are generally heated by a residual gas for about one third of the cycle time.
This regeneration is expensive in terms of energy. For example, for a 200 t/day air separation plant processing 30,000 m.sup.3 (s.t.p.)/h of air, a residual gas heater consumes 300 kW, i.e. an average of 100 kW.
One of the objects of this invention is to eliminate the independent heater, another object being to integrate the compression and regeneration systems in order to reduce the energy costs of the plant.